V-bearing titanomagnetite tails obtained after ore dressing are different from vanadium extraction tails and high titanium-content slags from blast furnace. They are a metallurgical waste which is very difficult to dispose of, and it is also a pollutant source resulting in serious environmental pollution. For example, since Panzhihua Iron and Steel (Group) Co. of China has been in production for 20 years, such tails discharged have amounted to more than 96 million tons. They not only polluted some of the river valley along the Jinshajiang River to the upper reaches of the Yangzi River, but also occupied a large area of land for storage.
Before the present invention, there have not been any methods for utilizing the V-bearing titanomagnetite tails obtained after ore dressing. Chinese patent application No. CN 85102464 discloses the utilization of waste residue obtained after vanadium-extraction by the method of atomization to produce the raw materials for ferrous metal oxide ceramic products and for black ceramic products manufactured by using said raw materials. Said raw materials are produced by using the industrial waste residue of natural ore having a total content of titanium, vanadium, chromium, manganese and iron over 20% by weight, or the industrial waste residue of natural ore having a total content of titanium, vanadium, chromium, and manganese over 30% by weight as base material, with or without additives. In particular, said industrial waste residues are the waste residue from vanadium-extraction or sintered slags from sulfurous iron ore and chromium slags. Using the raw materials as described in said patent application, only black ferrous metal oxide ceramics can be made. If they are used to produce architectural decorative preparations, their physical and chemical properties are superior to those of natural granite. However, they have the defects of dull coloring, high product density, obvious contraction during the sintering process, etc.
There are also literatures which report the utilization of waste slags from a blast furnace to manufacture raw materials for color ceramic products. For example, Chinese patent application No. CN 91107240.3 discloses a raw material for producing color ceramic products. The raw material is produced by using blast furnace slags containing 5-30% by weight TiO.sub.2 as base material, with or without additives and with or without coloring agents. The technical solution of said application has overcome the defects of low activity and difficulty of using blast furnace slag containing 5-30% by weight TiO.sub.2, which makes a TiO.sub.2 base material which is both colored and colors other material, and allows the base material to coordinate with additives or/and coloring agents. Therefore, metal oxide colored ceramic products having a series of colors can be prepared. When said raw materials are used for producing architectural decorative products, they also show better physical and chemical properties than those of natural granite. However, they can be sintered into the desired products only in a narrow temperature range, and tend to develop color differences during the sintering process. In addition, the blast furnace slags used as base material contain a lot of free iron and more soluble vanadium compounds (vanadates), and the shortcomings of this will be described hereinafter.
These two technical solutions of the above-mentioned applications, i.e., Chinese patent application Nos. CN 85102464 and CN 91107240.3 have their individual advantages and shortcomings, respectively. However, the raw materials for ceramic products described in these two applications have following common shortcomings.
1. The base materials contain more free iron. For example, the base material of CN 85102464 contains 3-5% by weight free iron and the base material of CN 91107240.3 contains 1-5% by weight free iron. The presence of free iron will prolong the duration of ball-milling of the base materials or the duration of processing. In addition, the products tend to bubble and/or form concavity during the sintering process. Finally, the products produced therefrom tend to crack during the cooling process.
2. The base materials contain more soluble vanadium compounds. The vanadium content of the base materials of CN 85102464 and CN 91107240.3 are in the range of 1-6% by weight, calculated on the basis of vanadium pentoxide, wherein, the former contains more than 0.55% by weight of soluble vanadium (vanadate) and the later contains more than 0.22% by weight of soluble vanadium(vanadate). During the sintering process, vanadium pentoxide and other high valence vanadium compounds decompose into low valence vanadium, and thus release oxygen, causing bubbles in the final products.
3. The base materials contain a certain quantity of sodium salt and potassium salt. Calculated on the basis of Na.sub.2 O and K.sub.2 O, the content of soluble sodium salts (sodium vanadate and sodium carbonate) is about 1-2% by weight and the content of soluble potassium salts (potassium vanadate and potassium carbonate) is more than 0.04% by weight. The presence of soluble sodium salts and potassium salts will result in cracks in the final products.